The present invention relates to network management in communications networks, and particularly although not exclusively to the detection of server layer re-configurations which affect client layers in a communications network operating a layered transmission protocol structure.
In prior art synchronous communications networks, for example of the synchronous digital hierarchy (SDH) type, incorporating synchronous optical network (SONET) options in accordance with ITU-T recommendation G.707, comprising a plurality of node equipment, communicating over a plurality of links, eg fiber optic links, reconfiguration of a network following physical modification to the network, for example addition or deletion of a node equipment, is carried out using a network management system comprising one or more graphical user interfaces, operated by one or more human network operators. In prior art network management systems, a network operator is presented with a visual display screen on a graphical user interface, displaying a plurality of icons representing node elements, links, connections and trails between node elements. Upon physical reconfiguration of part of a network, eg by reconnection of existing node elements in a different manner, or by addition or deletion of a node element, logical reconfiguration of the network including reconfiguration of routes, trails, connections is made by manual input of commands by a human network operator at the graphical user interface. For example, on adding a new node to an existing synchronous network, a network operator may visually inspect a two dimensional graphical visual representation of a section of a network on a visual display device, and by inspection of the visual display take a decision on how to re-route a trail or path in a synchronous network through a new node. Where the trail or path extends over a large number of nodes of the network, some of those nodes may be under control of a second network operator operating from a remote position. Under these circumstances, the two operators need to communicate with each other, eg by telephone, to discuss changes to the network, before implementing those changes by typing in keystroke commands at the respective graphical user interfaces of their network management systems.
However, prior art communications networks are highly complex in nature, typically operating a plurality of protocol layers comprising several server layers, eg physical layers and optical layers, and client layers, comprising service layers and the like. Changes to the server layers, such as physical replacement or reconfiguration of the node equipment or logical reconfiguration of one or more nodes at the server layers have consequences for reconfiguration of all client layers supported by those server layers. Thus, although the network operators are presented with a visual display at which visual representations of various client and server layers may be presented, due to the inherent size and complexity of communications networks, the impact of changes at the server layers may not be fully realized by human network operators, and reconfiguration of client layers upon changes to server layer functionality implemented by means of visual inspection by one or more network operators and manual entering of commands into a graphical user interface may not provide the optimum reconfiguration of a network. Although it may be possible to find reconfiguration solutions by visual inspection, a total range of possible reconfigurations is greater than a human operator can investigate. In order for the human network operator to produce any reconfiguration solution at all, this may entail a downtime on the corresponding part of the network from the order of around 10 minutes to days depending upon the complexity of connections to a node.
Further, prior art reconfigurations of synchronous networks operate only by using aggregates, and so re-routing solutions are found only when aggregates are de-multiplexed into tributaries.
One object of the present invention is to optimize the reconfiguration of a communications network at a set of clients layers, following a reconfiguration of the network at a server layer.
Another object of the present invention is to provide an automated network management tool for finding a plurality of possible reconfigurations of a communications network at a set of client layers, in consequence of a change or proposed change to a network at one or more server layers of the network.
A further object of the present invention is to enable a quicker time to reconfiguration of a network after changes to a network topology, either physical or logical.
Another object of the present invention is to find re-routing solutions in a network which are non-obvious to a human operator, or which would be practically impossible for a human operator to find.
According to a first aspect of the present invention there is provided a method of detecting an effect of a network topology change in a network comprising a plurality of resources arranged in a plurality of layers wherein resources at a client layer are dependent upon resources at a server layer, said method comprising the steps of: maintaining an object database describing a plurality of resources of said communications network, said object database comprising a plurality of instances representing physical and logical resources; modifying individual ones of said plurality of instances when a said resource is re-configured by setting a state of a said instance; and detecting at least one client layer resource affected by a change to a said server layer resource.
Said plurality of instances may include instances selected from the set: an instance representing a node entity; an instance representing an endpoint; an instance representing a trail; an instance representing a trail termination point; an instance representing a connection; an instance representing a connection termination point; an instance representing a link connection; an instance representing a port; an instance representing a sub network connection; an instance representing a link; an instance representing a link termination point.
Said method may comprise the steps of: receiving a signal for deletion of a trail; and in response to said received signal, reading said object database to determine whether a trail subject of said delete signal supports a client trail.
Said method may comprises the steps of: receiving a signal for deletion of a trail; on receipt of said delete signal determining whether a trail subject of said signal is supporting a client trail; and if said trail subject of said delete signal is supporting a client trail, setting a data describing said trail to a state signifying said trail is supporting at least one client trail.
The method may further comprise the step of setting data describing a said client trail to a state signifying deletion of said trail is inconsistent with supporting said client trail.
According to a second aspect of the present invention there is provided a method of re-routing a trail in a synchronous communications network, said method comprising the steps of: receiving a signal for creation of a new trail; for each of a pair of endpoints, identifying data describing said endpoint; determining whether said endpoint data is in a state signifying that said endpoint is capable of supporting said new trail and; if said endpoint data of each said endpoint is in a state signifying that said new trail can be created, creating said new trail.
According to a third aspect of the present invention there is provided a method of re-routing a client trail supported by a server trail, in a synchronous communications network, said method comprising the steps of: receiving a signal denoting that a new trail is to be created; identifying data describing at least one endpoint of said t rail to be created; determining from said endpoint data whether creation of said trail conflicts with another already created trail; and if said new trail to be created is in conflict with an already created trail, determining whether said already created trail is suitable for deletion.
Said method may further comprise the steps of, if said already created trail is in a state suitable for deletion, applying a search algorithm to search for an alternative route for routing said al ready created trail.
Said step of searching for an alternative route for said already created trail may comprise the steps of: assigning a cost data to each of a plurality of network resources; and determining an optimum route on the basis of said cost data.
For example, a said cost data may be assigned on the basis of an availability of a said network resource. A said cost data may be assigned on the basis of a least number of hops between node entities.
According to a fourth aspect of the present invention there is provided a method of managing a communications network comprising a plurality of network resources, said method comprising the steps of: representing each of a plurality of said network resources by managed object data in a managed object database; inputting signals describing deletion of a said resource at a server layer; interrogating said set of managed object data to find a set of client resources dependent on said server resource.
Said data describing said resources may comprise connection rule data describing a plurality of rules for connecting said plurality of resources.
Said plurality of network resources may include resources selected from the set: transmission entities; physical resources; logical resources.
Preferably said managed object data describes at least one element selected from the following set: trail termination point; connection termination point; connection; link; link connection; physical port; logical port; sub network connection; server trail; client trail; server link; client link.
The invention includes a network management apparatus for a communications systems comprising a plurality of nodes, said network management apparatus comprising: at least one data processor; at least one data storage means; wherein said processor and said data storage means are configured as a managed object database comprising a plurality of managed object data representing a plurality of resources of said communications network; and a said processor operates in accordance with an algorithm to detect changes to a configuration of said plurality of resources.
Preferably a said processor operates in accordance with an algorithm to find a plurality of routes across said network in response to a detected change of configuration of said plurality of resources.
Preferably a said processor operating in accordance with said detection algorithm operates to read a plurality of states of said managed objects of said managed object database.
A said topology change may comprise a physical topology change and/or a logical topology change. Topological changes may be made at a server layer of said network and said step of determining which of a plurality of nodes are affected comprises determining which of a set of client layer trails are affected.
Specific implementations of the present invention may provide an automated system capable of detecting when topology changes are made in a network and how those changes affect existing trail routings by changing a state of a data representation of components of a trail, eg endpoints, and data representing the trail itself to states denoting that a trail is in conflict with other trails (that is to say uses common end points or ports with other trails), and whether the trail supports other client trails at client layers.
Further, specific embodiments and implementations may be capable of detecting alternative routes for trails which may allow inconsistent trails in a xe2x80x9cdeleted supportingxe2x80x9d state to be re-routed. This may occur every time a topology change is made to a network and implementations may be capable of detecting a plurality of individual topological changes which occur independently throughout the network, and applying re-routing functionality for each individual occurrence of a topological change of the network. Specific implementations of the present invention may allow improved scalability of existing networks with minimum network management effort.
The invention is applicable generally, and particularly although not exclusively in the fields of synchronous digital hierarchy (SDH), synchronous optical network (SONET), asynchronous transfer mode (ATM), internet protocol, and frame relay.